PostgreSQL

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This page contains information about PostgreSQL the GitLab Support team uses when troubleshooting. GitLab makes this information public, so that anyone can make use of the Support team's collected knowledge.

WARNING: Some procedures documented here may break your GitLab instance. Use at your own risk.

If you're on a paid tier and aren't sure how to use these commands, contact Support for assistance with any issues you're having.

Start a database console

::Tabs

:::TabTitle Linux package (Omnibus)

Recommended for:

Single-node instances.
Scaled out or hybrid environments, on the Patroni nodes, usually the leader.
Scaled out or hybrid environments, on the server running the PostgreSQL service.

sudo gitlab-psql

On a single-node instance, or a web or Sidekiq node you can also use the Rails database console, but it takes longer to initialize:

sudo gitlab-rails db-console --database main

:::TabTitle Docker

docker exec -it <container-id> gitlab-psql

:::TabTitle Self-compiled (source)

Use the psql command that's part of your PostgreSQL installation.

sudo -u git -H psql -d gitlabhq_production

:::TabTitle Helm chart (Kubernetes)

If you run a hybrid environment, and PostgreSQL runs on a Linux packaged installation (Omnibus), the recommended approach is to use the database console locally on those servers. Refer to the details for Linux package.
Use the console that's part of your external third-party PostgreSQL service.
Run gitlab-rails db-console in the toolbox pod.
- Refer to our Kubernetes cheat sheet for details.

::EndTabs

To exit the console, type: quit.

Support topics

Database deadlocks

References:

Deadlocks can occur if an instance is flooded with pushes. Provided for context about how GitLab code can have this sort of unanticipated effect in unusual situations.

ERROR: deadlock detected

Three applicable timeouts are identified in the issue #30528; our recommended settings are as follows:

deadlock_timeout = 5s
statement_timeout = 15s
idle_in_transaction_session_timeout = 60s

Quoting from issue #30528:

"If a deadlock is hit, and we resolve it through aborting the transaction after a short period, then the retry mechanisms we already have will make the deadlocked piece of work try again, and it's unlikely we'll deadlock multiple times in a row."

NOTE: In Support, our general approach to reconfiguring timeouts (applies also to the HTTP stack) is that it's acceptable to do it temporarily as a workaround. If it makes GitLab usable for the customer, then it buys time to understand the problem more completely, implement a hot fix, or make some other change that addresses the root cause. Generally, the timeouts should be put back to reasonable defaults after the root cause is resolved.

In this case, the guidance we had from development was to drop deadlock_timeout or statement_timeout, but to leave the third setting at 60 seconds. Setting idle_in_transaction protects the database from sessions potentially hanging for days. There's more discussion in the issue relating to introducing this timeout on GitLab.com.

PostgreSQL defaults:

statement_timeout = 0 (never)
idle_in_transaction_session_timeout = 0 (never)

Comments in issue #30528 indicate that these should both be set to at least a number of minutes for all Linux package installations (so they don't hang indefinitely). However, 15 s for statement_timeout is very short, and is only effective if the underlying infrastructure is very performant.

See current settings with:

sudo gitlab-rails runner "c = ApplicationRecord.connection ; puts c.execute('SHOW statement_timeout').to_a ;
puts c.execute('SHOW deadlock_timeout').to_a ;
puts c.execute('SHOW idle_in_transaction_session_timeout').to_a ;"

It may take a little while to respond.

{"statement_timeout"=>"1min"}
{"deadlock_timeout"=>"0"}
{"idle_in_transaction_session_timeout"=>"1min"}

These settings can be updated in /etc/gitlab/gitlab.rb with:

postgresql['deadlock_timeout'] = '5s'
postgresql['statement_timeout'] = '15s'
postgresql['idle_in_transaction_session_timeout'] = '60s'

Once saved, reconfigure GitLab for the changes to take effect.

NOTE: These are Linux package settings. If an external database, such as a customer's PostgreSQL installation or Amazon RDS is being used, these values don't get set, and would have to be set externally.

Temporarily changing the statement timeout

WARNING: The following advice does not apply in case PgBouncer is enabled, because the changed timeout might affect more transactions than intended.

In some situations, it may be desirable to set a different statement timeout without having to reconfigure GitLab, which in this case would restart Puma and Sidekiq.

For example, a backup may fail with the following errors in the output of the backup command because the statement timeout was too short:

pg_dump: error: Error message from server: server closed the connection unexpectedly

You may also see errors in the PostgreSQL logs:

sudo gitlab-rails db-console --database main
```0

To temporarily change the statement timeout:

1. Open `/var/opt/gitlab/gitlab-rails/etc/database.yml` in an editor
1. Set the value of `statement_timeout` to `0`, which sets an unlimited statement timeout.
1. [Confirm in a new Rails console session](../operations/rails_console.md#using-the-rails-runner)
   that this value is used:

   ```shell
   sudo gitlab-rails runner "ActiveRecord::Base.connection_config[:variables]"

Perform the action for which you need a different timeout (for example the backup or the Rails command).
Revert the edit in /var/opt/gitlab/gitlab-rails/etc/database.yml.

Observe (RE)INDEX progress report

In some situations, you might want to observe the progress of a CREATE INDEX or REINDEX operation. For example, you can do this to confirm whether the CREATE INDEX or REINDEX operation is active, or to check which phase the operation is in.

Prerequisites:

You must use PostgreSQL version 12 or later.

To observe a CREATE INDEX or REINDEX operation:

Use the built-in pg_stat_progress_create_index view.

For example, from a database console session, run the following command:

sudo gitlab-rails db-console --database main
```1

To learn more about producing human-friendly output and writing data to log files, see [this snippet](https://gitlab.com/-/snippets/3750940).

## Troubleshooting

### Database is not accepting commands to avoid wraparound data loss

This error likely means that `autovacuum` is failing to complete its run:

```shell
sudo gitlab-rails db-console --database main
```2

Or

```shell
sudo gitlab-rails db-console --database main
```3

To resolve the error, run `VACUUM` manually:

1. Stop GitLab with the command `gitlab-ctl stop`.
1. Place the database in single-user mode with the command:

   ```shell
   /opt/gitlab/embedded/bin/postgres --single -D /var/opt/gitlab/postgresql/data gitlabhq_production

In the backend> prompt, run VACUUM;. This command can take several minutes to complete.
Wait for the command to complete, then press Control + D to exit.
Start GitLab with the command gitlab-ctl start.

GitLab database requirements

See database requirements and review and install the required extension list.

Serialization errors in the `production/sidekiq` log

If you receive errors like this example in your production/sidekiq log, read about setting default_transaction_isolation into read committed to fix the problem:

sudo gitlab-rails db-console --database main
```4

### PostgreSQL replication slot errors

If you receive errors like this example, read about how to resolve PostgreSQL HA
[replication slot errors](https://docs.gitlab.com/omnibus/settings/database.html#troubleshooting-upgrades-in-an-ha-cluster):

```shell
sudo gitlab-rails db-console --database main
```5

### Geo replication errors

If you receive errors like this example, read about how to resolve
[Geo replication errors](../geo/replication/troubleshooting/postgresql_replication.md):

```shell
sudo gitlab-rails db-console --database main
```6

### Review Geo configuration and common errors

When troubleshooting problems with Geo, you should:

- Review [common Geo errors](../geo/replication/troubleshooting/common.md#fixing-common-errors).
- [Review your Geo configuration](../geo/replication/troubleshooting/index.md), including:
  - Reconfiguring hosts and ports.
  - Reviewing and fixing the user and password mappings.

### Mismatch in `pg_dump` and `psql` versions

If you receive errors like this example, read about how to
[back up and restore a non-packaged PostgreSQL database](https://docs.gitlab.com/omnibus/settings/database.html#backup-and-restore-a-non-packaged-postgresql-database):

```shell
sudo gitlab-rails db-console --database main
```7

### Extension `btree_gist` is not allow-listed

Deploying PostgreSQL on an Azure Database for PostgreSQL - Flexible Server may result in this error:

```shell
sudo gitlab-rails db-console --database main
```8

To resolve this error, [allow-list the extension](https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/concepts-extensions#how-to-use-postgresql-extensions) prior to install.

PostgreSQL

Start a database console

Other GitLab PostgreSQL documentation

Procedures

Support topics

Database deadlocks

Temporarily changing the statement timeout

Observe (RE)INDEX progress report

GitLab database requirements

Serialization errors in the `production/sidekiq` log

PostgreSQL

Start a database console

Other GitLab PostgreSQL documentation

Procedures

Support topics

Database deadlocks

Temporarily changing the statement timeout

Observe (RE)INDEX progress report

GitLab database requirements

Serialization errors in the production/sidekiq log

Serialization errors in the `production/sidekiq` log